AbstractThe graft copolymerization of methyl methacrylate in wool fibers was investigated in the aqueous LiBr–K2S2O8system without homopolymer. The rate of grafting and the degree of polymerization of graft polymer were determined on varying the extent of reduction of wool fibers and the concentration of monomer. From the graft copolymerization behavior observed at a given concentration of redox catalysts (LiBr and K2S2O8), the thiol groups in wool fibers were considered to play a role as a sort of catalyst of polymerization, not as the chain transfer agent, and also to give the grafting sites. So, the initiation process of grafting was assumed to be started bydS·/dt=kiSHeff, and the kinetic consideration was found to lead to the following expression in agreement with the experimental results: 1/DP= (kt/kp2Mfib2)Rp, wheredS·/dtis the rate of formation of thiol radicals by radicalotropy to SH from SO4−., OH·, or Br·;ki,kp, andktare the rate constants of initiation, propagation, and termination, respectively; SHeffand Mfibare the concentration of the effective thiol groups and the MMA monomers within the wool fibers, respectively;DPis the average degree of polymerization of graft polymers, andRpthe overall rate of
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